Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 232016
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
216 PM MDT Mon Apr 23 2018

.SHORT TERM...(This evening through Wednesday night)
Issued at 330 PM MDT Mon Apr 23 2018

Tonight...Looks and feels like spring outside. Surface low pressure
continues to develop across our western counties with decent
pressure rises over northern Wyoming and decent pressure falls over
southeast Wyoming and western Nebraska. As a vigorous shortwave
trough aloft and its associated strong cold front pass our counties
the rest of today, expect increasing coverage of showers and
isolated thunderstorms, some of which may produce small hail and
wind gusts up to 50 mph based on shear and instability expectations.
Showers and thunderstorms will be most numerous over western
Nebraska this evening near the cold front with scattered showers
after midnight, mainly over western Nebraska.

Tuesday...Blustery and cold day as the shortwave trough aloft moves
slowly across western Nebraska with cold air advection at low levels
across our counties. Low and mid level gradients suggest a windy day
at most locations.

Tuesday night...Drying out period as the shortwave trough aloft
moves to northwest Kansas with decreasing cloud cover. Hard freeze
expected with cold airmass, clearing skies and light winds.

Wednesday...Much warmer with a transitory shortwave ridge aloft over
our counties and plenty of sunshine. With 700 mb temperatures rising
near 4 Celsius, expect maximum temperatures in the 60s at lower
elevations.

Wednesday night...Another cold frontal passage, mostly dry, as a
shortwave trough swings southeastward across the Dakotas. Orographic
type showers expected after midnight over the northern Laramie Range
and nearby portions of Converse County, otherwise dry. Not quite as
cold as the airmass recovers and mixing limits cooling.

.LONG TERM...(Thursday through Monday)
Issued at 330 PM MDT Mon Apr 23 2018

Weak cold front Thursday moves through the area during the day for
some light rainshowers. After this front moves through looking at
rising 500mb heights and warmer temperatures. By Saturday, 700mb
temperatures up to +8C. MEX guidance for Saturday showing 78 for a
high at Cheyenne and 80 for Sidney. Did go above guidance on
forecast temperatures.

Another shortwave possible for Sunday into Monday next week. GFS
further north over the ECMWF. That far out, confidence is low on
PoPs and the forecast track is sure to change between now and
then.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1012 AM MDT Mon Apr 23 2018

Introduced thunderstorms into the 18Z TAFs this afternoon. Latest
HRRR guidance showing earlier than expected development this
afternoon, so moved up timing as well. Possibility of seeing KCYS
going IFR as winds turn northeasterly shortly after 00Z. WIll
continue to monitor unfolding events.

&&

.FIRE WEATHER...
Issued at 230 PM MDT Mon Apr 23 2018

Cold front moving through southeast Wyoming this afternoon will
bring widespread wetting rains and mountain snow to the area.
Colder temperatures Tuesday before high pressure builds
in. Warmer temperatures should end out the week. With recent
rainfall and upcoming warm temperatures, would expect a rapid
acceleration of greenup across both southeast WYoming and
Nebraska Panhandle fire weather zones. Fire weather will not be a
concern this week.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&

$$

SHORT TERM...RUBIN
LONG TERM...GCC
AVIATION...GCC
FIRE WEATHER...GCC



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